1. Field of the Invention
Aspects of the present invention relate to a method and an apparatus for detecting and removing a false contour. The apparatus for detecting and removing the false contour can be applied to all devices obtaining, storing, or displaying a digital video, such as a digital multimedia broadcasting (DMB) player, a mobile communication terminal, a digital camera, a camera phone, a digital television (TV), and the like.
2. Description of the Related Art
There are many causes for occurrence of a false contour, however the false contour generally occurs when a quantization level is not sufficient. In this case, the quantization level indicates a brightness level. The quantization level is determined depending on a bit depth. As an example, although a false contour does not occur at an original bit depth, but when a video is converted, the false contour occurs at a lower bit depth. Also, the false contour occurs when the video is restored to the original bit depth. The false contour occurs when a video is compressed or restored, such as joint photographic experts groups (JPEG), and moving picture experts groups (MPEG), and the false contour also occurs in the case of contrast enhancement (CE) and detail enhancement (DE).
There are a blue noise mask method, a dithering method, and a Daly and Feng method as conventional methods for removing a false contour.
If a bit depth of an input video is less than a bit depth of an output video, the dithering method increases a bit depth as a result of an ordered matrix. However, the dithering method has a problem in that, an artificial pattern occurs in an entire video. Also, in the Daly and Feng method, a false contour is removed using a low pass filter (LPF) with respect to a video which has the false contour. The Daly and Feng method has a problem in that, a portion including the false contour is smoothed, and also a signal element which is identical to a real edge is blurred since the LPF is used with respect to an entire video. To solve the above mentioned problem, it is important to precisely find out a portion including the false contour.